Referring now to FIGS. 10, 11 and 12, a traditional micro switch 100′ is illustrated. As shown, the traditional micro switch 100′ comprises a coil 1′, an armature 2′, a release spring 3′, a return button 4′, a return spring 5′, a brake plate 6′, a balance frame 7′, a contact switch 8′ and a pull rod 9′, wherein the pull rod 9′ is a metal cylinder combined with the return button 4′ by hot casting. A lower end of the pull rod 9′ has a flange 91′ which has an upper surface 911′ and a lower surface 912′. The brake plate 6′ has a first lock hole 61′ and a second lock hole 62′, wherein the first lock hole 61′ has a right vertical surface 611′ and a left curved surface 612′. The balance frame 7′ has a first opening 71′ and a second opening 72′ formed along a longitudinal axis and a horizontal axis thereof, respectively. The pull rod 9′ is movably shifted upward and downward in the first opening 71′ along the longitudinal axis of the balance frame 7′. A portion of the brake plate 6′ having the first lock hole 61′ can be extended into the second opening 72′ and moved leftward and rightward.
When the traditional micro switch 100′ is in a release status, the left curved surface 612′ of the first lock hole 61′ of the brake plate 6′ is tightly abutted against a cone on the lower end of the pull rod 9′ due to an elastic return force of the release spring 3′. The lower end of the pull rod 9′ has the flange 91′, so that the return button 4′ can not be returned when the coil 1′ is not energized. During switching on the traditional micro switch 100′, the coil 1′, the armature 2′, the release spring 3′, the return button 4′, the return spring 5′, the brake plate 6′, the balance frame 7′, the contact switch 8′ and the pull rod 9′ must commonly coordinate with each other to move the balance frame 7′ upward. Then, the balance frame 7′ actuates a dynamic contact plate (not-shown) to move upward to be in contact with a static contact plate (not-shown), so as to finish switching on the traditional micro switch 100′.
However, the structure of the traditional micro switch 100′ is too complicated, and thus the installation thereof is difficult. To solve the shortcoming of the traditional micro switch 100′, the present invention designs a micro switch having simpler structures which thus can be conveniently installed.